Temperature effect on aerobic denitrification and nitrification

Nitrogen loss without organic removal in biofilter was observed and its possible reason was explained. A lower hydraulic loading could improve aerobic denitrification rate. Aerobic denitrification was seriously affected by low temperature(below 10℃). However, nitrification rate remained high when the temperature dropped from 15℃ to 5℃. It seemed the autotrophic biofilm in BAF could alleviate the adverse effect of low temperature.

Toxic effect of sodium perfluorononyloxy-benzenesulfonate on Pseudomonas stutzeri in aerobic denitrification,cell structure and gene expression

The toxicities of sodium perfluorononyloxy-benzenesulfonate(OBS)to animals and plants are similar to those of perfluorooctane sulfonate.However,the mechanism of its toxicity to aerobic denitrifying bacteria is still unclear.In the present study,the ecotoxicity of OBS on an aerobic denitrifying strain,Pseudomonas stutzeri,was evaluated.The results showed that a dosage of OBS clearly affected the growth and aerobic denitrification of P.stutzeri.When compared with an unamended control,the degradation efficiency of the total nitrogen decreased by 30.13%during exposure to 200 mg/L of OBS,and the complete degradation time of nitrate-nitrogen was delayed by 4 h.The lactate dehydrogenase and superoxide dismutase produced by the bacteria increased with the concentration of OBS,and reactive oxygen species were also detected by confocal laser scanning microscope imaging.Transmission electron microscope imaging revealed chromosome deformation of the cells and damage to cell content;moreover,outer membrane vesicles were secreted from the bacteria,which was the important detoxification mechanism of P.stutzeri to OBS.Expression of the genes involved in aerobic nitrification and oxidative stress were also changed under OBS stress,which further confirmed the toxicity of OBS to P stutzeri.This study reveals the environmental exposure risk of OBS from the perspective of microorganisms.

A heterotrophic nitrification-aerobic denitrification bacterium Halomonas venusta TJPU05 suitable for nitrogen removal from high-salinity wastewater

A novel salt-tolerant heterotrophic nitrification and aerobic denitrification(HN-AD)bacterium was isolated and identified as Halomonas venusta TJPU05(H.venusta TJPU05).The nitrogen removal performance of H.venusta TJPU05 in simulated water(SW)with sole or mixed nitrogen sources and in actual wastewater(AW)with high concentration of salt and nitrogen was investigated.The results showed that 86.12%of NH_(4)^(+)-N,95.68%of NO_(3)^(-)-N,100%of NO_(2)^(-)-N and 84.57%of total nitrogen(TN)could be removed from SW with sole nitrogen sources within 24 h at the utmost.H.venusta TJPU05 could maximally remove 84.06%of NH_(4)^(+)-N,92.33%of NO_(3)^(-)-N,92.9%of NO_(2)^(-)-N and 77.73%of TN from SW with mixed nitrogen source when the salinity was above 8%.The application of H.venusta TJPU05 in treating AW with high salt and high ammonia nitrogen led to removal efficiencies of 50.96%,47.28%and 43.19%for NH_(4)^(+)-N,NO_(3)^(-)-N and TN respectively without any optimization.Furthermore,the activities of nitrogen removal–related enzymes of the strain were also investigated.The successful detection of high level activities of ammonia oxygenase(AMO),hydroxylamine oxidase(HAO),nitrate reductase(NAR)and nitrite reductase(NIR)enzymes under high salinity condition further proved the HN-AD and salt-tolerance capacity of H.venusta TJPU05.These results demonstrated that the H.venusta TJPU05 has great potential in treating high-salinity nitrogenous wastewater.

Heterotrophic ammonium removal characteristics of an aerobic heterotrophic nitrifying-denitrifying bacterium, Providencia rettgeri YL

Bacterium Providencia rettgeri YL was found to exhibit an unusual ability to heterotrophically nitrify and aerobically denitrify various concentrations of ammonium （NH4^＋-N）. In order to further understand its removal ability, several experiments were conducted to identify the growth and ammonium removal response at different carbon to nitrogen （C/N） mass ratios, shaking speeds, temperatures, ammonium concentrations and to qualitatively verify the production of nitrogen gas using gas chromatography techniques. Results showed that under optimum conditions （C/N 10, 30℃, 120 r/min）, YL can significantly remove low and high concentrations of ammonium within 12 to 48 h of growth, respectively. The nitrification products hydroxylamine （NHzOH）, nitrite （NO2^-） and nitrate （NO3^-） as well as the denitrification product, nitrogen gas （N2）, were detected under completely aerobic conditions.

High nitrogen removal from wastewater with several new aerobic bacteria isolated from diverse ecosystems

Three new bacteria HS-03, HS-043 and HS-047 isolated from different ecosystems were found capable of aerobic denitrification. The potential application of these strains in wastewater treatment under aerobic conditions was investigated, These three bacteria all presented high nitrogen removal from wastewater that more than 98% of 10 mmol/L nitrate could be removed in 12--24 h by adding cheap external carbon source and low concentration of iron as well as molybdate. The mechanism at molecular level was analyzed. The success of this aerobic denitrification applied to wastewater treatment may serve as an alternative to enhance the practical nitrogen removal from wastewater. Main biochemical and physiological features of these strains were characterized. The 16S rDNA sequences were compared with the published data in GenBank by using BLAST. The results of phenotype and genotype proved that strain HS-03 and HS-047 belonged to Pseudomonas stutzeri and Pseudomonas pseudoalcaligenes respectively. Strain HS-043 was identified as Delftia clcidovorans of which denitrifying activity has not previously been explored.

Bioaugmentation of two-stage aerobic sequencing batch reactor with mixed strains for high nitrate nitrogen wastewater treatment

Mixed strains Delftia sp.YH01 and Acidovorax sp.YH02,with capability of heterotrophic nitrification-aerobic denitrification,were introduced into a two-stage aerobic sequencing batch reactor to enhance NO3^--N removal.With optimal C/N of 8,efficient NO3^--N removal was achieved at initial NO3^--N concentration of 2000 mg·L−1.Meanwhile,the massive accumulation of NO2^--N was avoided during the long operation.Compared to the one-stage aerobic sequencing batch reactor,the removal efficiency of NO3^--N and TN in the two-stage aerobic sequencing batch reactor was increased by 36.5% and 42.7%,which respectively was 93.8% and 88.4%.Microbial community study showed that the mixed strains have the stronger viability and can synergistically denitrify with the indigenous microorganisms in system,such as Azoarcus,Uncultured Saprospiraceae,Thauera,Paracocccus,which could be major contributors for aerobic denitrification.The proposed technology was shown to achieve high-efficiency treatment of high NO3^--N wastewater through aerobic denitrification.

POTENTIAL APPLICATION OF AN AEROBIC DENITRIFYING BACTERIUM AS BIOAGENTS FOR WASTEWATER TREATMENT

A bacterium strain HS-03 was isolated from the activated sludge plant in a suburb of Wuhan city, China which has been found to be capable of aerobic denitrification. The effect of different inoculated amounts of pre-cultured media was analyzed. The denitrifying rates of this strain under aerobic and micro-anaerobic conditions were compared. The result indicated that the rate was almost not affected by the presence of oxygen. 10m M nitrate was removed more than 90% in 36 hours by this bacterium in the specific medium. During the denitrifying process, nitrite was always kept at very low level. The denitrification potential of this bacterium was evaluated to treat artificial wastewater under fully aerobic conditions. Main biochemical and physiological features of this strain were characterized. The 16S rDNA sequence was compared with the published data in GenBank by using BLAST. The BLAST level of similarity to Pseudomonas stutzeri was 99.1%. These results of phenotype and genotype proved that the strain HS-03 was a new strain belonging to the species of P. stutzeri.

Denitrification characteristics of a marine origin psychrophilic aerobic denitrifying bacterium

A psychrophilic aerobic denitrifying bacterium,strain S1-1,was isolated from a biological aerated filter conducted for treatment of recirculating water in a marine aquaculture system.Strain S1-1 was preliminarily identified as Psychrobacter sp.based on the analysis of its 16S rRNA gene sequence,which showed 100% sequence similarity to that of Psychrobacter sp.TSBY-70.Strain S1-1 grew well either in high nitrate or high nitrite conditions with a removal of 100% nitrate or 63.50% nitrite,and the total nitrogen removal rates could reach to 46.48% and 31.89%,respectively.The results indicated that nitrate was mainly reduced in its logarithmic growth phase with a very low leve1 accumulation of nitrite,suggesting that the aerobic denitrification process of strain S1-1 occurred mainly in this phase.The GC-MS results showed that N 2 O was formed as the major intermediate during the aerobic denitrifying process of strain S1-1.Finally,factors affecting the growth of strain S1-1 and its aerobic denitrifying ability were also investigated.Results showed that the optimum aerobic denitrification conditions for strain S1-1 were sodium succinate as carbon source,C/N ratio15,salinity 10 g/L NaCl,incubation temperature 20°C and initial pH 6.5.

Isolation and characterization of heterotrophic nitrifying bacteria in MBR

The study presented the method for isolating the heterotrophic nitrifiers and the characterization of heterotrophic nitrification. Continuous tests via a membrane bioreactor (MBR) were operated under the controlled conditions to proliferate the nitrifiers. Heterotrophic nitrifying bacteria were isolated from the system in which the efficiency of total nitrogen(TN) removal was up to 80%. Since no autotrophic ammonium and nitrite oxidizers could be detected by fluorescence in situ hybridization(FISH), oxidized-N production was unlikely to be catalyzed by autotrophic nitrifiers during the heterotrophic nitrifiers' isolation in this study. The batch test results indicate that the isolated heterotrophic bacteria were able to nitrify. After 3 weeks incubation, the efficiencies of the COD removal by the three isolated bacterial strains B1, B2, and B3 were 52 6%, 71 7%, and 77 7%, respectively. The efficiencies of the TN removal by B1, B2, and B3 were 35 6%, 61 2% and 68 7%, respectively.

Screening and Characterization of Nitrite-Degrading Bacterial Isolates Using a Novel Culture Medium

In this study,a novel culture medium that simulates shrimp pond conditions was established to screen nitrite-degrading isolates.The medium was supplemented with nitrite as a nitrogen source and shrimp feed as the major carbon source,to achieve the high nitrogen and low carbon nutritional status found in shrimp farming ponds.Screening using this medium identified potent denitrifying Bacillus isolates,among which Bacillus subtilis M7-1 was considered best.M7-1 was able to completely degrade nitrite-N in 24 h without much consumption of dissolved oxygen.Efficient denitrification activity took place in liquid cultures within a set of non-stringent ranges of pH(5.0–9.0),salinity(0–30)and temperature(25–35℃).The denitrifying enzyme gene was amplified,sequenced and further identified as nirS type.In biosecurity assessments,M7-1 had no negative effects on shrimps at a dose of 106 cfu mL−1.M7-1 could therefore be used in aquaculture to reduce and control the nitrogen concentration,and to promote the development of sustainable and healthy culture systems.

Isolation and Characterization of a New Heterotrophic Nitrifying Bacillus sp. Strain

Objective To characterize the heterotrophic nitrifying bacteria. Methods The bacteria were isolated from membrane bioreactor for treating synthetic wastewater using the method newly introduced in this study. Fluorescence in situ hybridization （FISH） was used to validate the nonexistence of autotrophic ammonia oxidizers and nitrite oxidizers. Batch tests were carried out to investigate the capability of heterotrophic nitrification by the pure culture. Phylogenetic analysis of the pure culture was performed. Results A heterotrophic nitrifier, named Bacillus sp. LY, was newly isolated from the membrane bioreactor system in which the efficiency of TN removal was up to 80%. After 24-day, incubation, the removal efficiency of COD by Bacillus sp. LY was 71.7 %. The ammonium nitrogen removal rate after assimilation nearly ceased by Bacillus sp. LY was 74.7% The phylogenetic tree of Bacillus sp. LY and the neighbouring nitrifiers were given. Conclusions The batch test results indicate that Bacillus sp. LY can utilize the organic carbon as the source of assimilation when it grows on glucose and ammonium chloride medium accompanying the formation of oxidized-nitrogen. It also can denitrify nitrate while nitrifying. Bacillus sp. LY may become a new bacterial resource for heterotrophic nitrification and play a bioremediation role in nutrient removal.

The response of structure and nitrogen removal function of the biofilm on submerged macrophytes to high ammonium in constructed wetlands

The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands(CWs).The effects of high ammonium shocks on submerged macrophytes and epiphytic biofilms on the leaves of submerged macrophytes in CWs were rarely mentioned in previous studies.In this paper,the 16S rRNA sequencing method was used to investigate the variation of the microbial communities in biofilms on the leaves of Vallisneria natans plants while the growth characteristics of V.natans plants were measured at different initial ammonium concentrations.The results demonstrated that the total chlorophyll and soluble sugar synthesis of V.natans plants decreased by 51.45%and 57.16%,respectively,and malondialdehyde content increased threefold after8 days if the initial NH_(4)^(+)-N concentration was more than 5 mg/L.Algal density,bacterial quantity,dissolved oxygen,and pH increased with high ammonium shocks.The average removal efficiencies of total nitrogen and NH_(4)^(+)-N reached 73.26%and 83.94%,respectively.The heat map and relative abundance analysis represented that the relative abundances of phyla Proteobacteria,Cyanobacteria,and Bacteroidetes increased.The numbers of autotrophic nitrifiers and heterotrophic nitrification aerobic denitrification(HNAD)bacteria expanded in biofilms.In particular,HNAD bacteria of Flavobacterium,Hydrogenophaga,Acidovorax,Acinetobacter,Pseudomonas,Aeromonas,and Azospira had higher abundances than autotrophic nitrifiers because there were organic matters secreted from declining leaves of V.natans plants.The analysis of the nitrogen metabolic pathway showed aerobic denitrification was the main nitrogen removal pathway.Thus,the nitrification and denitrification bacterial communities increased in epiphytic biofilms on submerged macrophytes in constructed wetlands while submerged macrophytes declined under ammonium shock loading.

Effect of air-exposed biocathode on the performance of a Thauera-dominated membraneless single-chamber microbial fuel cell (SCMFC)

To investigate the effect of air-exposed biocathode（AEB） on the performance of singlechamber microbial fuel cell（SCMFC）, wastewater quality, bioelectrochemical characteristics and the electrode biofilms were researched. It was demonstrated that exposing the biocathode to air was beneficial to nitrogen removal and current generation. In Test 1 of 95%AEB, removal rates of ammonia, total nitrogen（TN） and chemical oxygen demand（COD）reached 99.34% ± 0.11%, 99.34% ± 0.10% and 90.79% ± 0.12%, respectively. The nitrogen removal loading rates were 36.38 g N/m3/day. Meanwhile, current density and power density obtained at 0.7 A/m3 and 104 m W/m3 respectively. Further experiments on opencircuit（Test 2） and carbon source（Test 3） indicated that this high performance could be attributed to simultaneous biological nitrification/denitrification and aerobic denitrification, as well as bioelectrochemical denitrification. Results of community analysis demonstrated that both microbial community structures on the surface of the cathode and in the liquid of the chamber were different. The percentage of Thauera, identified as denitrifying bacteria, maintained at a high level of over 50% in water, but decreased gradually in the AEB. Moreover, the genus Nitrosomonas, Alishewanella, Arcobacter and Rheinheimera were significantly enriched in the AEB, which might contribute to both enhancement of nitrogen removal and electricity generation.

Sustainable treatment of nitrate-containing wastewater by an autotrophic hydrogen-oxidizing bacterium

Bacteria are key denitrifiers in the reduction of nitrate(NO_(3)^(-)N),which is a contaminant in wastewater treatment plants(WWTPs).They can also produce carbon dioxide(CO_(2))and nitrous oxide(N2O).In this study,the autotrophic hydrogen-oxidizing bacterium Rhodoblastus sp.TH_(2)0 was isolated for sustainable treatment of NO_(3)^(-)N in wastewater.Efficient removal of NO_(3)^(-)N and recovery of biomass nitrogen were achieved.Up to 99%of NO_(3)^(-)N was removed without accumulation of nitrite and N2O,consuming CO_(2)of 3.25 mol for each mole of NO_(3)^(-)N removed.The overall removal rate of NO_(3)^(-)N reached 1.1 mg L^(-1)h^(-1)with a biomass content of approximately 0.71 g L^(-1)within 72 h.TH20 participated in NO_(3)^(-)N assimilation and aerobic denitrification.Results from 15N-labeled-nitrate test indicated that removed NO_(3)^(-)N was assimilated into organic nitrogen,showing an assimilation efficiency of 58%.Seventeen amino acids were detected,accounting for 43%of the biomass.Nitrogen loss through aerobic denitrification was only approximately 42%of total nitrogen.This study suggests that TH_(2)0 can be applied in WWTP facilities for water purification and production of valuable biomass to mitigate CO_(2)and N_(2)O emissions。